[英]Unique value Constraint with multiple columns across the table, not the combination in Oracle
在 oracle 中有沒有辦法在兩列之間強制唯一性?
它不是兩列組合之間的唯一性,而是兩列之間跨表的值。
參考:
不應允許的示例數據:
id | phone1 | phone2
1 | 111 | 111
id | phone1 | phone2
1 | 111 | NULL
2 | 111 | NULL
id | phone1 | phone2
1 | 111 | NULL
2 | NULL | 111
我的 Oracle 版本:
Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production
我會使用check()
約束來確保每一行的唯一性,以及跨行唯一性的唯一索引:
create table mytable (
id int,
phone1 int,
phone2 int,
check (phone1 <> phone2)
);
create unique index myidx on mytable(
greatest(coalesce(phone1, phone2), coalesce(phone2, phone1)),
least(coalesce(phone1, phone2), coalesce(phone2, phone1))
);
這種方法的好處是它還可以防止插入像(111, 222)
和(222, 111)
這樣的元組。
insert into mytable values(1, 111, 111);
ORA-02290: check constraint (FIDDLE_SMBYKTEIHNNVOHKZSCYK.SYS_C0020876) violated
begin
insert into mytable values(1, 111, null);
insert into mytable values(1, 111, null);
end;
/
ORA-00001: unique constraint (FIDDLE_SMBYKTEIHNNVOHKZSCYK.MYIDX) violated ORA-06512: at line 3
begin
insert into mytable values(1, 111, null);
insert into mytable values(1, null, 111);
end;
/
ORA-00001: unique constraint (FIDDLE_SMBYKTEIHNNVOHKZSCYK.MYIDX) violated ORA-06512: at line 3
begin
insert into mytable values(1, 111, 222);
insert into mytable values(1, 222, 111);
end;
/
ORA-00001: unique constraint (FIDDLE_SMBYKTEIHNNVOHKZSCYK.MYIDX) violated ORA-06512: at line 3
我會結合檢查約束和 function 上的唯一索引來解決它:
CREATE TABLE t(id NUMBER, phone1 NUMBER, phone2 NUMBER);
ALTER TABLE t ADD CONSTRAINT c1 CHECK (phone1 <> phone2);
CREATE UNIQUE INDEX u ON t(COALESCE(phone1, phone2));
案例1作品:
INSERT INTO t VALUES (1, 111, 111);
ORA-02290: check constraint (C1) violated
案例 2 也有效:
INSERT INTO t VALUES (1, 111, NULL);
INSERT INTO t VALUES (2, 111, NULL);
ORA-00001: unique constraint (U) violated
案例3,同樣:
INSERT INTO t VALUES (1, 111, NULL);
INSERT INTO t VALUES (2, NULL, 111);
ORA-00001: unique constraint (WFL.U) violated
但是,這不受保護:
INSERT INTO t VALUES (1, 111, 222);
INSERT INTO t VALUES (2, 222, 111);
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